您可以使用自定义URL字段来修改每个库图像的附件链接：

以下插件支持此操作：

<?php
/**
 * Plugin Name:   Custom Attachments Links
 * Description:   Adds a new media field, to override the default attachment links.
 * Plugin URI:    http://wordpress.stackexchange.com/a/176668/26350
 * Plugin Author: Birgir Erlendsson (birgire)
 * Version:       0.0.1
 */

add_filter( \'attachment_fields_to_edit\', function( $fields, $post )
{
    $fields[\'wpse_custom_attachment_url\'] = array(
        \'label\' => \'Custom URL\',
        \'input\' => \'text\',
        \'value\' => get_post_meta( $post->ID, \'wpse_custom_attachment_url\', true ),
        \'helps\' => "Override the attachment\'s default",
    );
    return $fields;
}, 10, 2 );

add_filter( \'attachment_fields_to_save\', function( $post, $attachment )
{
    if( isset( $attachment[\'wpse_custom_attachment_url\'] ) )
        update_post_meta( 
            $post[\'ID\'], 
            \'wpse_custom_attachment_url\', 
            $attachment[\'wpse_custom_attachment_url\'] 
        ); 
    return $post;
}, 10, 2 );

! is_admin() && add_filter( \'attachment_link\', function( $link, $pid )
{
    if( $url = get_post_meta( $pid, \'wpse_custom_attachment_url\', true ) )
        $link = esc_url( $url );   
    return $link;
}, 10, 2 );